1. Field of the Invention
The present invention relates to an ink jet recording apparatus for forming image information such as an ink image onto the recording medium such as a recording sheet or a plastic sheet using the ink, and more particularly to stabilization of the temperature of a head member which is carried on said ink jet recording apparatus.
2. Related Background Art
Recording apparatuses having the features of printer, copying machine and facsimile, or employed as the output device for the composite electronic equipment or workstation containing a computer, a word processor and so on, are configured to record the image onto the recording medium such as a paper or a plastic thin plate based on image information. Such recording apparatuses can be classified into an ink jet system, a wire dot system, a thermal system, and a laser beam system, according to the recording method.
Among the above-cited recording apparatuses, a recording apparatus adopting the ink jet system (ink jet recording apparatus), which performs the recording by discharging the ink from recording means (recording head) onto the recording medium, has the advantages that recording means can be made compact, the high definition image can be recorded at high speed, the ordinary paper is usable for recording without needs of any special treatment, the running cost is lower, there is less noise owing to the non-impact method, and the color image is easy to record by using the color ink. In particular, a line-type recording apparatus employing recording means of line type where a number of discharge ports are arranged in a direction of sheet width allows the faster recording to be effected.
Specifically, recording means (recording head) of the ink Jet system of discharging the ink by the use of heat energy can be easily fabricated with an arrangement of liquid channels (discharge ports) at high density by forming electrothermal converters, electrodes, liquid channel walls, and a ceiling plate as the film on a substrate through a semiconductor fabrication process including etching, vapor deposition and sputtering, and thus the apparatus can be made more compact. It is noted that the electrothermal converters are usually supported on a metallic support plate (base plate), and secured at respective predetermined locations. The base plate also serves as the heat sink to radiate the heat generated in the recording head.
In recent years, however, the high speed data processing has been allowed owing to the higher speed of CPU and the greater capacity of memory, resulting in the increased amount of discharging the ink per unit time (hereinafter referred to as duty). That is, the energy entered into the conventional recording head per unit time is steadily increasing because of the higher discharge frequency or more nozzles required for the faster recording, as well as the greater recording duty owing to the color recording or graphic recording associated with the replenished software environment (OS, application), resulting in increased calorific power from the recording head. When the temperature of this recording head is elevated beyond a certain value, there was a risk that the recording head might be degraded on the performance, as well as on the safety, resulting in lower recording quality.
To overcome the above-described problem, it is considered that the base plate attached to the recording head and also serving as the heat sink is made larger, but it is difficult to realize from the respects of increased cost, the ecology (larger consumption goods, or larger parts which are less reproducible), and the larger apparatus, resulting in a problem that the requirements for the faster recording and the color recording in the future are difficult to deal with.